1. Field of the Invention
The invention relates to a radiator or heater having flat tubes arranged in parallel and connected to header or manifold pipes for feed and return flow, in which tubes support parts for transmitting the welding pressure and are arranged in the region of the connecting bores on the mutually opposite inner walls.
2. Description of the Prior Art
A radiator of this kind has been proposed in which the header pipes are arranged on the rear of the flat tubes which are coplanar and are connected to the header pipes by means of projection welding. In this rational manufacturing technique all the connections can be produced at the same time, the one electrode of a welding machine being pressed against the header pipes and the other electrode against the flat tubes, with a pressure of up to 800 kg. In order that the flat tubes are not deformed thereby, support parts bearing upon the opposite inner walls of the flat tube are arranged within the flat tubes in the region of each of the connecting bores. To enable the projection welding method to be used, in the known radiator or heater it was proposed to press a zone of the wall surrounding each connecting bore of the header pipes or the flat tubes outwardly so that the projection welding can be carried out with the thus produced section protruding frusto-conically from the surface of the tube or pipe (Swiss Pat. No. 592,290).
According to another, earlier proposal, intermediate bush-like pieces are welded into the flat tubes at every connecting bore, which pieces extend through the whole of the interior of the flat tubes and protrude to one side beyond these, so that they can take up the welding pressure to be applied in projection welding, and the protruding ends of these intermediate pieces can be attached at the same time for all connections to the header pipes by means of projection welding. This method, however, has the disadvantage that the intermediate pieces to be inserted into the flat tubes have to be welded into the flat tubes by means of oxy-acetylene or CO.sub.2 welding.
For the production of such a radiator the flat tubes, which are manufactured in long lengths, must be cut to the desired length in each case and closed at the ends, if the header pipes are to be attached to the rear of the flat tubes. The problem of the closure of the ends of the flat tubes is eliminated in other known types of construction of radiators where the flat tubes open at their ends into the header pipes arranged on the end. In the initially mentioned known radiators the flat tubes are closed at their ends by a welded-in cover following the fitting of the support parts, which have to be arranged previously at every connecting bore, into the flat tube. This method requires much skill and is not very economical. When especially flat tubes are used, their ends can also be closed by welding of the previously inwardly bent marginal zones of the tube walls which lie closely opposite one another by reason of the small internal width. This, however, again requires a prior deformation of the flat tube ends.